U.S. patent number 4,045,718 [Application Number 05/564,638] was granted by the patent office on 1977-08-30 for multiple winding multiple voltage alternator electrical supply system.
This patent grant is currently assigned to Maremont Corporation. Invention is credited to Alden J. Gray.
United States Patent |
4,045,718 |
Gray |
August 30, 1977 |
Multiple winding multiple voltage alternator electrical supply
system
Abstract
A multiple voltage electrical supply system continuously
connected for individually charging a plurality of battery supplies
continuously connected in series with one another to supply a
plurality of load circuits having differing d.c. input voltage
requirements and, typically, also having differing expected
electrical power consumption rates. The system includes an
alternator having electrically isolated generating windings
disposed so as to insure that the magnetic flux linking each of the
generating windings bears a substantially constant ratio to that
linking the other of the generating windings. The exemplary
embodiment has generating windings of different characteristic
resistance per unit length such that there is an increased internal
voltage drop in the winding intended to supply the lighter
electrical load. The resultant voltage regulation characteristics
are such that a single voltage regulator is sufficient to maintain
both of the output voltages at a substantially constant
predetermined ratio.
Inventors: |
Gray; Alden J. (Ashfield,
MA) |
Assignee: |
Maremont Corporation (Saco,
ME)
|
Family
ID: |
24255291 |
Appl.
No.: |
05/564,638 |
Filed: |
April 2, 1975 |
Current U.S.
Class: |
320/123; 310/198;
307/16; 322/90 |
Current CPC
Class: |
H02J
7/1423 (20130101); H02K 19/34 (20130101) |
Current International
Class: |
H02J
7/14 (20060101); H02K 19/34 (20060101); H02K
19/16 (20060101); H02J 007/14 (); H02M
007/00 () |
Field of
Search: |
;322/28,90 ;310/198
;320/15,17,64,65,61 ;307/16 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hickey; Robert J.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
What is claimed is:
1. A multiple voltage electrical supply system continuously
connected for individually charging a plurality of battery supplies
continuously connected in series with one another to supply a
plurality of load circuits having differing d.c. input voltage
requirements, said load circuits also having differing expected
electrical power consumption rates such that one of said battery
supplies is normally expected to draw less charging current than
the other of said battery supplies, said system comprising:
an alternator structure including,
a stator means having salient poles of ferromagnetic material,
a rotor means magnetically coupled and rotably mounted with respect
to said stator means and shaped so as to cause variations of
magnetic flux within said salient poles in response to rotation
thereof,
a field winding mounted to generate magnetic flux in said rotor and
stator means in response to electrical current flow in said field
winding,
a first generating winding disposed upon said salient poles of a
first electrical conductor having a first characteristic resistance
per unit length and producing a first a.c. output therefrom in
response to rotation of said rotor means due to the magnetic flux
variations produced thereby,
a second generating winding electrically isolated from said first
winding, said second winding also being disposed upon said salient
poles so as to insure that the magnetic flux linking said first
generating winding bears a substantially constant ratio to the
magnetic flux linking said second generating winding,
said second generating winding being formed of a second conductor
having a second characteristic resistance per unit length greater
than said first characteristic resistance per unit length thereby
producing an increased internal voltage drop in said second winding
as compared to said first winding for a given current flow, said
second winding producing a second a.c. output therefrom in response
to rotation of said rotor structure due to the magnetic flux
variations produced thereby;
a first rectifier means continuously connected to said first
generating winding and converting said first a.c. output into a
corresponding first d.c. output which is, in turn, continuously
connected to provide charging current to the said other of said
battery supplies requiring the relatively greater expected charging
current;
a second rectifier means continuously connected to said second
generating winding and converting said second a.c. output into a
corresponding second d.c. output which is, in turn, continuously
connected to provide charging current to the said one of said
battery supplies requiring the relatively smaller expected charging
current; and
a single voltage regulator connected to sense the voltage at one of
said first and second d.c. outputs an also connected to control the
current flow in said field winding so as to maintain the voltage at
said selected one of the d.c. outputs at a desired level and
thereby also substantially maintain the voltage at the remaining
d.c. output at a corresponding desired voltage level as a result of
the relatively greater expected current to be drawn from said first
generating winding and the increased internal voltage drop in said
second generating winding as compared to said first generating
winding for a given current flow due to the increased internal
winding resistance of said second generating winding as compared to
said first generating winding.
2. A multiple voltage electrical supply system as in claim 1
wherein:
said first generating winding comprises a three-phase winding
producing a three-phase first a.c. output;
said second generating winding comprises a single phase winding
producing a single phase second a.c. output; said first rectifier
means comprises a three-phase full wave rectifier; and
said second rectifier means comprises a single phase full wave
rectifier.
3. A multiple voltage electrical supply system as in claim 1
wherein:
said first and second generating means are each three-phase
windings producing three-phase first and second a.c. outputs
respectively; and
said first and second rectifier means are each three-phase full
wave rectifiers.
4. A multiple voltage electrical supply system for use with a
plurality of load circuits having differing d.c. input voltage
requirements, said system comprising:
an alternator having a plurality of sets of generating windings
producing a corresponding plurality of a.c. output voltages,
at least one of said sets of generating windings being formed of
differently sized conductors than another of said sets of
generating windings,
a plurality of rectifiers, each continuously connected with a
respective one of said sets of generating windings, for rectifying
said plurality of a.c. output voltages into a corresponding
plurality of d.c. voltages,
a plurality of batteries continuously connected in series with one
another, each of said batteries having two terminals,
a plurality of load circuits continuously connected across
different pairs of said terminals of said series connected
batteries so as to receive different d.c. voltages from said
batteries,
conductor means continuously connecting each of said plurality of
d.c. voltages from said plurality of rectifiers across two
respectively associated terminals of an individual respectively
associated one of said batteries,
said alternator having a magnetic flux conducting ferromagnetic
core carrying said sets of generating windings and also having a
field coil, the degree of excitation of which controls the total
amount of magnetic flux passing through said core and the amplitude
of the a.c. voltages induced in the windings of said sets of
windings,
said windings being mounted on said core in such a manner that a
substantially constant ratio of magnetic flux magnetically links
each of the sets of windings when compared to one another, and
a single voltage regulator means responsive to the electrical
output from a corresponding single one of said sets of generating
windings for controlling the excitation of said field coil and
maintaining the electrical output voltages from all of said sets of
generating windings at substantially constant values without
changing any electrical interconnections between said winding,
rectifiers, batteries or load circuits
the relative construction, size and disposition of said sets of
generating windings being effective to automatically maintain
substantially constant output voltages from all sets of generating
windings in response to regulation from said single voltage
regulator means while, at the same time, automatically varying the
charging current produced from said sets of generating windings as
required by the respectively corresponding connected batteries.
5. A multiple voltage electrical supply system as defined in claim
4 further characterized by each winding of one of said sets having
a corresponding winding in each of the other sets and said
ferromagnetic core of said alternator including a plurality of
salient poles, corresponding windings of said sets of generating
windings being mounted on the same one of said salient poles.
6. A dual voltage electrical system comprising:
an alternator having a first set of generating windings producing a
first a.c. output voltage and also having a second set of
generating windings electrically isolated from said first set of
windings and producing a second a.c. output voltage:
said first set of generating windings being formed of differently
sized conductors than said second set of generating windings,
a first rectifier for rectifying said first a.c. output voltage
into a first d.c. voltage, said first rectifier having first and
second output terminals across which said first d.c. voltage
appears,
a second rectifier for rectifying said second a.c. output voltage
into a second d.c. voltage, said second rectifier having third and
fourth output terminals across which said second d.c. voltage
appears,
said second and third terminals being of opposite polarity,
conductor means electrically connecting said second and third
terminals to one another continuously at a common point,
a first battery continuously connected between said first terminal
and said common point,
a second battery continuously connected between said common point
and said fourth terminal,
a service load circuit connected across said first terminal and
said common point so as to be in parallel with said first
battery,
a second load circuit requiring a higher input voltage than said
service load circuit connected across said first and fourth
terminals so as to be connected in parallel with the series
combination of said two batteries,
said alternator having a magnetic flux conducting ferromagnetic
core carrying said first and second sets of generating windings and
also having a field coil,
each winding of one of said sets having a corresponding winding in
the other of said sets and each winding and its corresponding
winding being mounted on said core in such a manner that
substantially all of the magnetic flux which passes through any one
winding also passes through its corresponding winding and so that
the voltage induced in one winding has a fixed ratio to the voltage
induced in its corresponding winding, and
a single voltage regulator responsive to the d.c. output voltage
appearing across the two output terminals of one of said two
rectifiers for controlling the excitation of said field coil to
maintain said latter d.c. output voltage at a substantially
constant value
the relative construction, size and disposition of said sets of
generating windings being effective to automatically maintain
substantially constant output voltages from all sets of generating
windings in response to regulation from said single voltage
regulator means while, at the same time, automatically varying the
charging current produced from said sets of generating windings as
required by the respectively corresponding connected batteries.
7. A dual voltage electrical system as defined in claim 6 further
characterized by said core having a plurality of salient poles each
of which receives one of said windings of said first set of
generating windings and its corresponding winding of said second
set.
8. A dual voltage electrical system as defined in claim 6 further
characterized by an internal combustion engine for driving said
alternator, an electrical starter motor for starting said engine,
and at least one electrically powered accessory associated with
said engine, said accessory comprising at least a part of said
service load circuit and said starter motor comprising at least a
part of said second load circuit.
9. A multiple voltage electrical supply system for use with a
plurality of load circuits having differing d.c. input voltage
requirements, said system comprising:
an alternator having a plurality of sets of generating windings
producing a corresponding plurality of a.c. output voltages,
a plurality of rectifiers, each continuously connected with a
respective one of said sets of generating windings, for rectifying
said plurality of a.c. output voltages into a corresponding
plurality of d.c. voltages,
a plurality of batteries continuously connected in series with one
another, each of said batteries having two terminals,
a plurality of load circuits continuously connected across
different pairs of said terminals of said series connected
batteries so as to receive different d.c. voltages from said
batteries,
conductor means continuously connecting each of said plurality of
d.c. voltages from said plurality of rectifiers across two
respectively associated terminals of an individual respectively
associated one of said batteries,
said alternator having a magnetic flux conducting ferromagnetic
core carrying said sets of generating windings and also having a
field coil, the degree of excitation of which controls the total
amount of magnetic flux passing through said core and the amplitude
of the a.c. voltages induced in the windings of said sets of
windings,
said windings being mounted on said core in such a manner that a
substantially constant ratio of magnetic flux magnetically links
the sets of windings,
a single voltage regulator means responsive to the electrical
output from a corresponding single one of said sets of generating
windings for controlling the excitation of said field coil and
maintaining the electrical output voltages from all of said sets of
generating windings at substantially constant values without
changing any electrical interconnections between said windings,
rectifiers, batteries or load circuits,
each winding of one of said sets having a corresponding winding in
each of the other sets and said ferromagnetic core of said
alternator including a plurality of salient poles, corresponding
windings of said sets of generating windings being mounted on the
same one of said salient poles, and
said alternator being an inductor alternator wherein said field
coil, said core and said sets of generating windings are stationary
relative to one another, said inductor alternator including a part
of ferromagnetic material rotatable relative to said core for
varying the reluctance of the flux paths through said salient poles
of said core to in turn vary the amount of flux passing through
said salient poles and the voltages induced in the windings on said
poles.
10. A multiple voltage electrical supply system for use with a
plurality of load circuits having differing d.c. input voltage
requirements, said system comprising:
an alternator having a plurality of sets of generating windings
producing a corresponding plurality of a.c. output voltages,
a plurality of rectifiers, each continuously connected with a
respective one of said sets of generating windings, for rectifying
said plurality of a.c. output voltages into a corresponding
plurality of d.c. voltages,
a plurality of batteries continuously connected in series with one
another, each of said batteries having two terminals,
a plurality of load circuits continuously connected across
different pair of said terminals of said series connected batteries
so as to receive different d.c. voltages from said batteries,
conductor means continuously connecting each of said plurality of
d.c. voltages from said plurality of rectifiers across two
respectively associated terminals of an individual respectively
associated one of said batteries,
said alternator having a magnetic flux conducting ferromagnetic
core carrying said sets of generating windings and also having a
field coil, the degree of excitation of which controls the total
amount of magnetic flux passing through said core and the amplitude
of the a.c. voltages induced in the windings of said set of
windings,
said windings being mounted on said core in such a manner that a
substantially constant ratio of magnetic flux magnetically links
the sets of windings,
a single voltage regulator means responsive to the electrical
output from a corresponding single one of said sets of generating
windings for controlling the excitation of said field coil and
maintaining the electrical output voltages from all of said sets of
generating windings at substantially constant values without
changing any electrical interconnections between said windings,
rectifiers, batteries or load circuits,
each winding of one of said sets having a corresponding winding in
each of the other sets and said ferromagnetic core of said
alternator including a plurality of salient poles, corresponding
windings of said sets of generating windings being mounted on the
same one of said salient poles, and
said corresponding windings of said sets being wound in multifilar
relationship with one another.
11. A multiple voltage electrical supply system for use with a
plurality of load circuits having differing d.c. input voltage
requirements, said system comprising:
an alternator having a plurality of sets of generating windings
producing a corresponding plurality of a.c. output voltages,
a plurality of rectifiers, each continuously connected with a
respective one of said sets of generating windings, for rectifying
said plurality of a.c. output voltages into a corresponding
plurality of d.c. voltages,
a plurality of batteries continuously connected in series with one
another, each of said batteries having two terminals,
a plurality of load circuits continuously connected across
different pairs of said terminals of said series connected
batteries so as to receive different d.c. voltages from said
batteries,
conductor means continuously connecting each of said plurality of
d.c. voltages from said plurality of rectifiers across two
respectively associated terminals of an individual respctively
associated one of said batteries,
said alternator having a magnetic flux conducting ferromagnetic
core carrying said sets of generating windings and also having a
field coil, the degree of excitation of which controls the total
amount of magnetic flux passing through said core and the amplitude
of the a.c. voltages induced in the windings of said sets of
windings,
said windings being mounted on said core in such a manner that a
substantially constant ratio of magnetic flux magnetically links
the sets of windings,
a single voltage regulator means responsive to the electrical
output from a corresponding single one of said sets of generating
windings for controlling the excitation of said field coil and
maintaining the electrical output voltages from all of said sets of
generating windings at substantially constant values without
changing any electrical interconnections between said windings,
rectifiers, batteries or load circuits,
each winding of one of said sets having a corresponding winding in
each of the other sets and said ferromagnetic core of said
alternator including a plurality of salient poles, corresponding
windings of said sets of generating windings being mounted on the
same one of said salient poles, and
each of said sets of generating windings including three groups of
windings in which electrical voltages of different phases are
induced, the three groups of windings of each set being connected
to one another to produce a three-phase a.c. output voltage, and
each of said rectifiers being a three-phase rectifier for
rectifying the three-phase a.c. voltage from the associated set of
generating windings into a d.c. voltage.
12. A dual voltage electrical system comprising: an alternator
having a first set of generating windings producing a first a.c.
output voltage and also having a second set of generating windings
electrically isolated from said first set of windings and producing
a second a.c. output voltage,
a first rectifier for rectifying said first a.c. output voltage
into a first d.c. voltage, said first rectifier having first and
second output terminals across which said first d.c. voltage
appears,
a second rectifier for rectifying said second a.c. output voltage
into a second d.c. voltage, said second rectifier having third and
fourth output terminals across which said second d.c. voltage
appears,
said second and third terminals being of opposite polarity,
conductor means electrically connecting said second and third
terminals to one another continuously at a common point,
a first battery continuously connected between said first terminal
and said common point,
a second battery continuously connected between said common point
and said fourth terminal,
a service load circuit connected across said first terminal and
said common point so as to be in parallel with said first
battery,
a second load circuit requiring a higher input voltage than said
service load circuit connected across said first and fourth
terminals so as to be connected in parallel with the series
combination of said two batteries,
said alternator having a magnetic flux conducting ferromagnetic
core carrying said first and second sets of generating windings and
also having a field coil,
each winding of one of said sets having a corresponding winding in
the other of said sets and each winding and its corresponding
winding being mounted on said core in such a manner that
substantially all of the magnetic flux which passes through any one
winding also passes through its corresponding winding and so that
the voltage induced in one winding has a fixed ratio to the voltage
induced in its corresponding winding, and
a single voltage regulator responsive to the d.c. output voltage
appearing across the two output terminals of one of said two
rectifiers for controlling the excitation of said field coil to
maintain said latter d.c. output voltage at a substantially
constant value,
said windings of said first set windings being in bifilar
relationship with the corresponding windings of said second set of
windings.
13. A dual voltage electrical system comprising:
an alternator having a first set of generating windings producing a
first a.c. output voltage and also having a second set of
generating windings electrically isolated from said first set of
windings and producing a second a.c. output voltage,
a first rectifier for rectifying said first a.c. output voltage
into a first d.c. voltage, said first rectifier having first and
second output terminals across which said first d.c. voltage
appears,
a second rectifier for rectifying said second a.c. output voltage
into a second d.c. voltage, said second rectifier having third and
fourth output terminals across which said second d.c. voltage
appears,
said second and third terminals being of opposite polarity,
conductor means electrically connecting said second and third
terminals to one another continuously at a common point,
a first battery continuously connected between said first terminal
and said common point,
a second battery continuously connected between said common point
and said fourth terminal,
a service load circuit connected across said first terminal and
said common point so as to be in parallel with said first
battery,
a second load circuit requiring a higher input voltage than said
service load circuit connected across said first and fourth
terminals so as to be connected in parallel with the series
combination of said two batteries,
said alternator having a magnetic flux conducting ferromagnetic
core carrying said first and second sets of generating windings and
also having a field coil,
each winding of one of said sets having a corresponding winding in
the other of said sets and each winding and its corresponding
winding being mounted on said core in such a manner that
substantially all of the magnetic flux which passes through any one
winding also passes through its corresponding winding and so that
the voltage induced in one winding has a fixed ratio to the voltage
induced in its corresponding winding, and
a single voltage regulator responsive to the d.c. output voltage
appearing across the two output terminals of one of said two
rectifiers for controlling excitation of said field coil to
maintain said latter d.c. output voltage at a substantially
constant value,
said alternator being an inductor alternator wherein said
ferromagnetic core, said field coil and said two sets of generating
windings are fixed relative to one another and wherein changes in
the magnetic flux passing through said two sets of generating
windings on said ferromagnetic core are produced by a ferromagnetic
part rotatable relative to said core.
14. A dual voltage electrical system comprising:
an alternator having a first set of generating windings producing a
first a.c. output voltage and also having a second set of
generating windings electrically isolated from said first set of
windings and producing a second a.c. output voltage,
a first rectifier for rectifying said first a.c. output voltage
into a first d.c. voltage, said first rectifier having first and
second output terminals across which said first d.c. voltage
appears,
a second rectifier for rectifying said second a.c. output voltage
into a second d.c. voltage, said second rectifier having third and
fourth output terminals across which said second d.c. voltage
appears,
said second and third terminals being of opposite polarity,
conductor means electrically connecting said second and third
terminals to one another continuously at a common point,
a first battery continuously connected between said first terminal
and said common point,
a second battery continuously connected between said common point
and said fourth terminal,
a service load circuit connected across said first terminal and
said common point so as to be in parallel with said first
battery,
a second load circuit requiring a higher input voltage than said
service load circuit connected across said first and fourth
terminals so as to be connected in parallel with the series
combination of said two batteries,
said alternator having a magnetic flux conducting ferromagnetic
core carrying said first and second sets of generating windings and
also having a field coil,
each winding of one of said sets having a corresponding winding in
the other of said sets and each winding and its corresponding
winding being mounted on said core in such a manner that
substantially all of the magnetic flux which passes through any one
winding also passes through its corresponding winding and so that
the voltage induced in one winding has a fixed ratio to the voltage
induced in its corresponding winding,
a single voltage regulator responsive to the d.c. output voltage
appearing across the two output terminals of one of said two
rectifiers for controlling the excitation of said field coil to
maintain said latter d.c. output voltage at a substantially
constant value, and
said first set of windings being made of conductor having a smaller
resistance per unit length than the conductor comprising said
second set of windings.
Description
This invention generally relates to a multiple voltage electrical
supply system for supplying a plurality of d.c. voltages. More
particularly, it relates to a multiple voltage electrical supply
system of a type which is especially useful for individually
charging a plurality of battery supplies in a vehicular or other
electrical system associated with a prime mover (i.e. a stationary
power plant) which requires a first d.c. operating voltage for a
conventional "service load" (e.g. 12 volts for lighting,
instrumentation, etc.) and a higher second d.c. voltage for
operating a special load (e.g. 24 volts for a cranking motor).
Typically, a single 12 volt battery or two series connected six
volt batteries are utilized for supplying a twelve volt service
load while two twelve volt batteries connected in series or four
six volt batteries connected in series are utilized for supplying
the 24 volt starter motor circuitry. The 12 volt service load may,
of course, be supplied by two or more battery supplies connected in
parallel if desired.
Such dual voltage electrical systems have been used in some types
of vehicles for many years as the required cranking power for
starting such vehicles has increased. For a time, such requirements
for a dual voltage vehicle electrical system were minimized by
attempts to design higher powered output 12 volt starting motors.
However, for various reasons, there now appears to be an even
greater demand for higher voltage cranking motors and, as a
consequence, the resulting dual voltage vehicular electrical
system.
Of course, the battery supply of d.c. voltage for such dual voltage
systems must be replenished by a suitable battery charging
arrangement which, in turn, obtains its energy input from a prime
mover such as an internal combustion engine which is often the same
prime mover as that utilized by the vehicle for locomotion. As will
be appreciated by those in the art, it is desirable to provide a
single alternator or generator structure and to have that single
alternator or generator structure properly charge all of the
batteries in the system so as to maintain a required dual voltage
supply for the service load and the starting motor.
The most common practice in the past has been to provide a
so-called "series-parallel" switch arrangement whereby two twelve
volt battery supplies are normally connected in parallel for
charging by a twelve volt supply of charging current from an
alternator or a generator structure driven by the prime mover. The
service load would, of course, also be connected across the
normally parallel connected batteries. However, in a starting
switch position, the "series-parallel" switch would reconnect the
batteries in series with the starter motor circuit so as to supply
that circuit with a higher 24 volts. As is recognized in the art,
there are many practical maintenance problems with such
"series-parallel" switches in part because of mechanical
complexities of the switch, mechanical wear, and the high
electrical cranking currents that must be carried by the electrical
contacts of such a switch, etc.
Accordingly, there have been a number of prior suggestions for
achieving the desired dual voltage system without using the
"series-parallel" switch wherein the two twelve volt batteries
involved in the dual voltage system are permanently connected in
series with one another and charged by a generating system driven
by the prime mover which provides two isolated d.c. outputs
supplying charging currents for the batteries. However, as those in
the art will also appreciate, reliable and effective practical
achievement of such a system is complicated by the fact that the
battery supplying the service load normally requires much higher
charging currents than the auxiliary battery which is normally used
only during operation of the starter motor and by the fact that
these two unequal electrically isolated charging currents must be
produced by a single alternator or generator structure since it is
not considered desirable to mount two completely separate
alternator structures on the prime mover.
One prior art attempt to achieve such a dual voltage supply system
without the "series-parallel" switch is shown by U.S. Pat. No.
3,710,226 issued to Seike, Jan. 9, 1973. Here, the three-phase
generating winding of a standard alternator has been reconnected
such that only two phases are utilized for supplying charging
current to the main battery and the third electrically isolated
phase of the generating winding is output separately to supply
charging current for the auxiliary battery. The usual voltage
regulator is utilized for regulating the output voltage delivered
to charge the main battery by regulating the current through a
field winding of the alternator while a special solid state series
regulator is utilized for controlling the output charging voltage
delivered to the auxiliary battery. However, this prior art
arrangement requires two separate voltage regulator circuits and,
in addition, necessarily increases the ripple component of charging
currents supplied to the two batteries since the main battery is
only supplied by two phases and the auxiliary battery is supplied
by but a single phase of the alternator generating windings.
Another prior art approach is shown by U.S. Pat. No. 3,816,805
issued to Terry on June 11, 1974. In this prior art approach, one
phase of the three-phase electrical output from the alternator is
also utilized to energize the primary winding of an isolation
transformer while the secondary of the isolation transformer then
provides an isolated source of a.c. output which is rectified in a
single phase full wave rectifier and utilized for charging the
auxiliary battery.
Still another prior art approach is shown by U.S. Pat. No.
3,793,544 issued to Baumgartner et al on Feb. 19, 1974. Here, the
usual three-phase generating windings of the alternator have been
duplicated to provide two electrically isolated but otherwise
identical sets of generating windings in the same alternator
structure. The two a.c. electrical outputs from these isolated
generating windings are then individually rectified and utilized
for supplying charging currents to the two serially connected
batteries in the dual voltage system. However, Baumgartner, et al
recognizes that one of the batteries will inherently require
greater amounts of charging currents than the other thus spoiling
the voltage regulation of the two output voltages from the system
unless special precautions are taken. Baumgartner et al teaches
such special precautions in the form of circuitry which attempts,
insofar as possible, to maintain a balanced loading of both
alternator generating windings. A special detector control
circuitry is provided to detect any unbalanced loading of the
multiple windings and, in response thereto, to actuate a relay coil
and switching contacts which changes the current path for the
service load and battery charging currents in an attempt to keep
the system balanced sufficiently to permit operating with a single
voltage regulator which controls a single field winding in the
alternator. As will be appreciated, this approach involves the
utilization of extra circuitry and, in addition, a special relay
switching contact for switching potentially high currents in
response to changes in the load balance.
Now, however, it has been discovered that the invention to be
described below provides a simplified yet improved multiple voltage
electrical supply system for such a dual voltage system which
permits the batteries to remain connected permanently or
continuously and, in addition, permits permanent or continuous
individual charging connections to be maintained with both of the
batteries while, at the same time, providing ample voltage
regulation of both output voltages from the system with but a
single voltage regulator circuit operating off one of the two
outputs from the system to control the current through a field
winding of a special alternator structure.
In essence, the invention to be described below approaches the
general problem of the dual voltage system as described above from
a different perspective than that of the known prior art as
discussed above. For instance, this invention includes a special
alternator structure having isolated sets of generating windings
for supplying two electrically isolated a.c. outputs that are
subsequently rectified to provide the necessary isolated d.c.
outputs for charging the two serially connected batteries in the
dual voltage system. However, rather than taking pains to equalize
the loading of such multiple generating windings as attempted by
Baumgartner et al, it is recognized at the outset that the two
generating windings involved will be unequally loaded in normal
operation. Recognizing and accepting this fact, the system of this
invention is advantageously capable of making an advantage out of
this feature to result in a properly voltage regulated system using
only a single voltage regulator circuit which is nevertheless
continuously connected for individually charging the plurality of
battery supplies which are, in turn, continuously connected in
series with one another to supply a plurality of load circuits
having differing d.c. requirements. Since the load circuits in
question normally have differing expected electrical power
consumption rates, one of the supplies will normally be expected to
draw less charging current than the other. Accordingly, under the
teachings of this invention, the wire size of the generating
winding included for supplying such a reduced charging current is
made smaller than the other winding thus producing a higher
internal winding resistance for this winding. Since the internal
winding resistance is higher for the auxiliary winding, the
internal voltage drop in the auxiliary winding can be made equal to
the internal voltage of the main winding even though different
average current levels are to be expected in the two windings.
Accordingly, a single voltage regulator may still be utilized for
effectively regulating the outputs of both generating windings even
though there is no special detecting circuitry or relay switching
contacts, etc., as proposed in the past for solving this
problem.
The alternator structure utilized in the exemplary embodiment of
this invention includes a stator means having salient poles of
ferromagnetic material, a rotor means magnetically coupled and
rotatably mounted with respect to the stator means and shaped so as
to cause variations of magnetic flux within the salient poles in
response to rotation thereof and a field winding mounted to
generate magnetic flux in the rotor and stator means in response to
electrical current flow therethrough. First and second generating
windings are disposed upon the salient poles of the stator means
with both the first and second windings being electrically isolated
from one another. In the exemplary embodiment, the electrical
conductor comprising the first generating winding has a certain
characteristic resistance per unit length associated therewith
while the electrical conductor associated with the second winding
has a different and greater characteristic resistance per unit
length. The first and second generating windings produce
respectively corresponding first and second a.c. outputs therefrom
in response to rotation of the rotor means due to the magnetic flux
variations produced thereby.
The first and second generating windings of the stator means are
disposed with respect to one another so as to insure that the
magnetic flux linking the first generating winding bears a
substantially constant ratio to the magnetic flux linking the
second generating winding. In one of the preferred exemplary
embodiments, this constant ratio is substantially one where both of
the windings are similarly disposed three-phase generating
windings. However, another exemplary embodiment is also disclosed
wherein the first winding is a three-phase winding and the second
generating winding is a single phase winding. In this case, the
ratio flux linking the first generating winding to that flux which
also links the second generating winding would be less than one but
would nevertheless be a substantially constant ratio such that the
voltage generated by flux changes within the rotor and stator means
in the two generating coils would, similarly, bear a substantially
constant ratio.
Since the second generating winding in the exemplary embodiment is
formed of the second conductor material having a second and higher
characteristic resistance per unit length than the first generating
winding, it follows that an increased internal voltage drop is
produced in the second winding as compared to the first winding for
a given current flow thus, even though the second winding will be
called upon to produce a lower expected charging current with the
auxiliary battery, the voltage regulation of its charging current
will compare quite favorably with the voltage regulation achieved
in the first generating winding which has a lower internal
resistance and a higher average current output.
This invention provides a multiple voltage electrical supply system
for powering a number of d.c. loads having different voltage and/or
load requirements. The system includes a number of battery supplies
(each battery supply may itself comprise a plural combination of
batteries such as, for instance, two twelve volt batteries
connected in parallel or two six volt batteries connected in
series, etc.) connected in series with one another to provide at
their various terminals a number of different d.c. voltage levels
which may be tapped to power a number of d.c. loads of different
voltage requirements. An alternator is provided having a number of
electrically isolated sets of generating windings with each set
producing a three-phase or other alternating current output
voltage. A like number of rectifiers individually rectify the a.c.
outputs of the respectively corresponding various sets of
generating windings and each rectifier applies its d.c. output
across a respectively associated one of the battery supplies. The
alternator has a core of ferromagnetic material carrying the sets
of generating windings. Each winding set is so mounted to the
alternator core that a substantially constant ratio of the magnetic
flux which passes through one winding set also passes through other
corresponding winding sets with the result that the voltages which
are induced in the sets of windings also bear a substantially
constant ratio one to another. Accordingly, the d.c. output
voltages from the various rectifiers retain the same ratio relative
to one another despite changes in the load imposed on any one
rectifier, the ratio being one-to-one in the case where each
winding of one set has a corresponding winding or windings in the
other set or sets and the windings of one set have the same number
of turns as the windings of the other set to which it is compared.
A voltage regulator senses the output voltage of one of the
rectifiers and adjusts the excitation of a field coil to maintain
the sensed output voltage at a desired pre-selected level. Because
of the nature of the inductive coupling between the various sets of
alternator windings and the substantially constant ratios mentioned
above, the output of the other rectifier or rectifiers is
automatically maintained substantially at its desired level through
the regulation of the output of the first rectifier. This desired
regulation is also enhanced by another feature of the invention,
namely the inclusion of a higher internal winding resistance for
the windings connected to supply the relatively lesser charging
current.
Preferably, each winding of one set of windings and its
corresponding winding or windings in the other set or sets of
windings are wound on the core of the alternator in a bifilar,
trifilar, quadrifilar or other multifilar manner, depending on the
number of sets of windings involved, wherein the conductor of one
winding and the conductor or conductors of the corresponding
winding or windings run side-by-side with one another throughout
the length of each winding. Further, the alternator is preferably
an inductor alternator having salient poles on which the generating
windings are received, the field coil, core and generating windings
being fixed relative to one another and changes in the magnetic
flux through the generating windings being produced by a
ferromagnetic part rotated relative to the core. Also, the
generating windings of the alternator are preferably of large
diameter wire and few turns to reduce the voltage drop across each
coil due to its impedance and the current flowing therethrough.
However, if it is known that one winding will normally carry more
current than its corresponding windings, the one carrying the
smaller amount of current is preferably made of a smaller diameter
to achieve a closer regulation of the voltages of the corresponding
windings as explained above.
In a specific form, the invention resides in a high voltage start,
lower voltage charge electrical system for a vehicle with a battery
started internal combustion engine wherein two batteries are
continuously connected in series with one another. A starter motor
is connected across the series combination of the two batteries and
a service load is connected across only one of the two batteries.
The alternator has two sets of generating windings, the outputs of
which are respectively rectified by two rectifiers, and the output
of each rectifier is continuously connected and applied across a
respective one of the two batteries.
As will now be appreciated, the invention provides a system having
a minimum of complexity and in which two or more isolated and
voltage regulated d.c. output voltages are respectively connected
across two or more series connected batteries so that each of the
batteries is charged individually upon individual demand. Further,
the invention provides a system which eliminates expensive or
failure prone components such as mechanical or solid state relays
or switches and transformers. The mounting space required for these
components is also eliminated. Further, the invention provides a
multiple voltage electrical supply system wherein good regulation
of a plurality of output d.c. voltages is obtained, despite
differences in the values of the electrical loads served by such
output voltages, and wherein only a single voltage regulator is
required for such regulation.
It especially should be noted that although in the presently
preferred and herein illustrated embodiment of the invention the
system is a dual voltage system utilizing an alternator with two
sets of windings, two rectifiers and two batteries, the invention
is not necessarily limited to such a dual voltage situation and,
instead, any larger number of d.c. output voltages may be
accommodated by increasing the number of sets of alternator
windings, the number of rectifiers and the number of batteries in
accordance with the general teaching of this application.
These and other objects and advantages of the invention will be
more completely understood from the following detailed description
of the preferred embodiments and the accompanying drawings of
which:
FIG. 1 is a schematic block diagram illustrating a complete
electrical system embodying this invention and in combination with
an internal combustion engine;
FIG. 2 is another schematic circuit diagram showing portions of the
FIG. 1 diagram in more detail;
FIG. 3 is a schematic circuit diagram illustrating in even more
detail part of the system shown in FIG. 1;
FIG. 4 is a fragmentary view generally similar to the right-hand
portion of FIG. 3 showing how the system of FIG. 3 may be modified
by the connection thereto of a second service load circuit;
FIG. 5 is a fragmentary perspective view showing the manner in
which the windings of the alternator are wound on their poles in a
bifilar manner.
FIG. 6 is a vertical longitudinal section view taken through the
alternator of FIG. 1;
FIG. 7 is a vertical transverse sectional view taken on the line
7--7 of FIG. 6;
Referring to the drawings, FIG. 1 shows an electrical supply
system, indicated generally at 10, embodying this invention and
used in conjunction with an internal combustion engine 12, a
service load 14 and a starter motor 16 controlled by a switch 18.
In a common instance, the engine 12 may be that of a truck, bus or
other large motor vehicle and the service load 14 may be a load
circuit which includes all of the electrical components and
accessories of the vehicle such as lights, etc., which are designed
to require a standard d.c. supply voltage, commonly 12 volts. The
starter motor 16, when energized, cranks the engine 12 for starting
purposes and requires a higher supply voltage than the service load
14. In particular, the illustrated exemplary starter motor 16 is
taken to be one designed for a 24 volt d.c. supply voltage.
The electrical supply system 10 of FIG. 1 includes an alternator 20
driven by the engine 12 when the engine is running. When driven,
the alternator 20 produces two electrically isolated a.c. outputs
appearing respectively on the lines 22 and 24. The a.c. output on
the line 22 is rectified by a first rectifier 26 to produce a d.c.
output voltage which appears across two output terminals 28 and 30
of the rectifier, the terminals 28 and 30 sometimes being referred
to hereinafter as first and second terminals, respectively.
Likewise, the a.c. output appearing on the line 24 is rectified by
a second rectifier 32 to produce a second d.c. output voltage which
appears across two output terminals 34 and 36 of the rectifier, the
terminals 34 and 36 sometimes being hereinafter referred to as
third and fourth terminals, respectively. The second terminal 30
and third terminal 34, which are of opposite polarity, are
connected to a common point 38.
The supply system 10 also includes two battery supplies 40 and 42.
Within the broader aspects of the invention, the two batteries may
be of various different voltage ratings and/or battery combinations
depending on the requirements of the service load and starter motor
circuit with which they are used; but, in the illustrated case,
each battery supply is taken to be a single twelve volt battery in
keeping with the explanatory assumption that the service load is
one requiring a twelve volt input and the starter motor one
requiring a 24 volt input. The battery 40 has its positive terminal
connected to the common point 38 and its negative terminal
connected to the first rectifier terminal 28 through the line 44
which is also shown as being grounded to the vehicle chassis. The
battery 42 has its negative terminal connected to the common point
38 and its positive terminal connected to the fourth rectifier
terminal 36 through the line 46. As will be appreciated all the
exemplary polarities (except for the field coil connection) would
be reversed for a "positive ground" vehicular electrical
system.
From the foregoing description together with a further study of
FIG. 1, it will be observed that the service load 14 if connected
across the battery 40 so as to be energized by the twelve volt d.c.
voltage normally appearing across such battery, whereas the starter
motor 16 is connected across the series combination of the two
batteries 40 and 42 so as to be energized, when the starter motor
switch 18 is closed, by the 24 volt d.c. voltage normally appearing
across the two batteries. Also, the d.c. output voltage from the
rectifier 26 is connected across only the first battery 40 and the
d.c. output voltage from the rectifier 32 is connected across only
the second battery 42. Therefore, the two batteries 40 and 42 are
individually charged by the two rectifiers and, as will hereinafter
become apparent, the load imposed on either one of the rectifiers
has substantially no effect on the output of the other rectifier so
that each battery is charged on an individual demand basis.
The output voltage of the first rectifier 26 is sensed by a voltage
regulator 48 which conventionally controls the alternator 20 in
such a manner as to keep the sensed voltage at a desired value.
Preferably the regulator 48 also includes an a.c. input from the
alternator so as to prevent the passage of field coil current
unless the alternator rotor is being rotated. The output voltage of
the second rectifier, due to the construction of the alternator 20,
as hereinafter discussed, automatically follows the output voltage
of the first rectifier so that when one output voltage is
regulated, as by the regulator 48, the other output voltage is
inherently regulated without another separate regulator being
needed.
FIG. 2 is similar to FIG. 1 except that mechanical connections to
the internal combustion engine 12 are not indicated and the
internal electrical characteristics of the alternator 20 are
depicted in more detail.
Here, a first generating winding is depicted by an internal voltage
source V.sub.1 and an internal winding resistance R.sub.1 while a
second generating winding is depicted by an internal voltage source
V.sub.2 and an internal winding resistance R.sub.2. Internal
reactive impedances for the windings are ignored for the present
explanatory purposes since, in the preferred embodiment, both
windings are magnetically linked with a coupling coefficient of
substantially one thus effectively automatically equalizing the
reactive components of internal voltage drops in the two
windings.
Since auxiliary battery 42 normally requires a relatively small
charging current compared with the required charging current for
battery 40, it follows that I.sub.2 will be normally less than
I.sub.1. Thus, by properly choosing R.sub.2 to be greater than
R.sub.1, the normally expected voltage regulation for the first and
second windings can be closely matched despite the unequal loading
thereof. As one possible example, providing acceptable dual
regulation, the first winding may have three phases each formed
from approximately #9 round copper wire while the second winding
may have three corresponding phases each formed from approximately
#20 round copper wire to provide a nominal load capacity of 30-40
amperes per phase for I.sub.1 and 8-10 amperes per phase for
I.sub.2.
FIG. 3 shows in more detail an exemplary form of the electrical
supply system of FIG. 1. Referring to FIG. 3, the alternator 20 is
shown to be a three-phase alternator having one three-phase
alternating current output appearing on three conductors comprising
the line 22 of FIG. 1 and also having a second three-phase
alternating current output appearing on three conductors
constituting the line 24 of FIG. 1. One or both of these windings
could be a single or other phase winding if three-phase operation
is not deemed necessary or desirable for some reason. In any event,
two separate alternating current outputs are produced by the two
separate electrically isolated sets of generating windings in the
alternator. In FIG. 3, the generating windings of one set are each
indicated by the reference numeral 50 with the reference numeral
having the subscript a, b or c added to indicate the phase group to
which the winding belongs. That is, the windings 50a, 50a
constitute a second phase group, and the windings 50c, 50c
constitute a third phase group of the first set of generating
windings. Likewise, the reference numeral 52 has been used to
indicate each of the windings of the second set of generating
windings with the subscripts a, b and c being added to indicate the
phase group to which such windings belong. The number of windings
in each set may vary without departing from the invention, but in
the illustrated case, each set of windings includes twelve windings
divided into three phase groups of four windings each group.
In the preferred exemplary embodiment, each winding 50 of the first
set of windings has a corresponding winding 52 in the second set of
windings. Further, each winding and its corresponding winding is so
mounted on the flux carrying ferromagnetic core of the alternator
that the magnetic flux which passes through any one winding also
passes through its corresponding winding to produce an effective
coupling coefficient of one. Other specific arrangements may also
be utilized so long as the arrangement maintains a substantially
constant ratio between flux linking one winding set and that
linking another winding set. Thus, the voltage induced in any one
winding by the varying flux is also induced in its corresponding
winding (or a predetermined ratio thereof in the case of less than
a unity coupling), provided each winding has the same number of
turns. In the exemplary alternator of FIG. 3, the windings of each
set are assumed to have the same number of turns as the
corresponding windings of the other set so that the three-phase
voltage applied to the rectifier 26 by the first set of windings
over the line 22 corresponds almost exactly with the three-phase
voltage supplied to the rectifier 32 over the line 24.
The rectifier 26 is preferably a full wave rectifier consisting, in
the case of three-phase a.c., of six diodes 54, 54. The rectifier
32 is likewise preferably a full wave rectifier consisting, in the
case of three-phase a.c., of six diodes 56, 56. The alternator 20
includes a field coil 58, the excitation of which is controlled by
the regulator 48 to vary the total magnetic flux passing through
parts of the alternator as required to maintain the d.c. output
voltage of the first rectifier 26 at a desired constant value.
The actual construction of the alternator 20 may vary widely. It
is, however, preferably a salient pole inductor alternator, and
FIGS. 6 and 7 show one preferred form thereof. The inductor
alternator shown by these figures is identical to the one shown and
described in a copending commonly assigned U.S. Pat. application
Ser. No. 360,908, filed May 16, 1973, except for each stator pole
of the alternator receiving two generating windings rather than one
generating winding. Another preferred exemplary embodiment for the
salient pole inductor is described in detail in copending commonly
assigned U.S. pat. application Ser. No. 522,294, filed Nov. 8,
1974. Reference may, therefore, be had to said copending
applications for further details of the alternator construction.
For the present, it is sufficient to note that the alternator 20,
in FIGS. 6 and 7 consists of a stator structure made up of a frame
or housing 60, an annular ferromagnetic stator core 62 having an
annular series of stator poles 63, 63, and a field coil 58, the
housing 60 having an annular cavity in which the field coil 58 and
core 62 are received. A rotor 64, fixed to a shaft 66 and rotatable
relative to the stator structue, includes an annular ferromagnetic
rotor core 68 which is received in the annular space between the
radially outwardly facing pole faces of the stator core poles 63,
63 and the radially inwardly facing housing surface 70 defining
part of the housing cavity. The rotor core 68 includes a plurality
of radially inwardly extending poles 72, 72 which cooperate with
the stator poles 63, 63 as the rotor rotates, to cyclicly vary the
amount of flux passing through each stator pole and to accordingly
induce alternating voltages in the windings received on the stator
poles.
In the alternator 20, each stator pole 63 receives one winding 50
of the first set of generating windings and a corresponding winding
52 of the second set of generating windings. In FIGS. 6 and 7 the
windings 50 and 52 are shown in such a way as to suggest that each
of the two windings on any given pole 63 is separate from the other
with the windings being radially stacked on the pole. Such a
construction may be used if desired. Preferably, however, the two
windings 50 and 52 of each pole are wound in a bifilar manner as
shown illustratively in FIG. 5.
Referring to FIG. 5, the winding 50 is formed of one conductor 74
and the winding 52 is formed of another conductor 76. The two
conductors 74 and 76 are disposed directly adjacent to one another
and run side-by-side throughout the length of each conductor. That
is, in the winding process, the two conductors are laid
side-by-side and wound simultaneously as if a single strand.
Therefore, the two windings 50 and 52 are intimately associated
with one another and the possibility of one winding experiencing a
different flux change than the other winding, due for example to
leakage of flux from the associated pole 63 at different points
along the length of the pole, is substantially eliminated. In FIG.
5, each winding 50 and 52 is shown to constitute only a few number
of turns but, of course, in actual practice each winding
constitutes a far greater number of turns. Also, of course, each
winding 50 and 52 is electrically insulated from one another as by
a suitable insulating coating on each of the conductors 74 and 76
making up the windings. Still further, the conductor used for one
set of generating windings 50, 50 is preferably of a different
gauge and therefore of a different resistance per unit length than
the conductor used for the other set of generating windings 52, 52
to suit different power requirements imposed on the two different
sets of windings by the loads to which they are connected a
described above.
Having now described in detail a dual voltage electrical supply
system embodying the invention, with reference to FIGS. 1 to 7, its
operation may be briefly summarized by noting that when the engine
12 and alternator 20 of FIG. 1 are stopped, the battery 40 supplied
twelve volt d.c. electrical power to any components or accessories
of the service load 14 as may be turned on. Also, when the starter
motor 16 is energized to crank the engine 12, power is drawn from
both of the batteries 40 and 42 which in series combination provide
a 24 volt d.c. input to the motor. After the engine 12 is started
and the alternator 20 driven at a normal operating speed, the
rectifier 26 provides a d.c. output voltage which both charges the
battery 40 and supplies the service load 14. The second rectifier
32 in turn produces a d.c. output voltage which charges the battery
42. The output voltages from both of the rectifiers are maintained
at the desired voltage level by the voltage regulator 48 which
senses only the output of the rectifier 26 but which nevertheless
also regulates the output of the rectifier 32 due to the coupling
of the two output voltages resulting from the bifilar or similar
arrangement of the two sets of generating windings in the
alternator 20 and/or the relative sizing of internal winding
resistances and expected load currents as described above.
FIGS. 1-3 show only a single service load supplied by the
illustrated dual voltage supply system. The system is not, however,
limited to use with such a single service load and, if desired, a
second service load, electrically isolated from the first service
load may be attached to and supplied by the system. Such an
arrangement is shown in FIG. 4 wherein the first load 14 is, as
previously described, connected across the battery 40 and wherein a
second service load 78 is connected across the second battery
42.
While only a few exemplary embodiments of this invention have been
described in detail above, those in the art will recognize that
many modifications and variations of the exemplary embodiments are
possible without materially departing from the novel teachings and
improvements of this invention. Accordingly, all such modifications
and variations of the exemplary embodiments are intended to be
included within the scope of this invention as defined by the
appended claims.
* * * * *